Answers:
(i) Artery and vein:
Arteries:
Muscular blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.
Vein:
A blood vessel that carries blood toward the heart. The majority of veins in the body carry lowoxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
(ii) Hard water and soft water:
Hard water:
Water that has a high mineral content (contrast with soft water), usually consisting of calcium (Ca2+) and magnesium (Mg2+) ions, and possibly including other dissolved metals, bicarbonates, and sulfates. Calcium usually enters the water as either calcium carbonate (CaCO3) in the form of limestone and chalk, or calcium sulfate (CaSO4) in the form of other mineral deposits. The predominant source of magnesium is dolomite (CaMg(CO3)2). Hard water is generally not harmful.
Soft water:
The term used to describe types of water that contain few or no calcium or magnesium ions.
The term is usually relative to hard water, which does contain significant amounts of such ions.
(iii) E-mail and Snail mail:
E-Mail:
Method of correspondence via the Internet; communication sent by electronic mail.
Snail Mail:
Regular mail, normal postal service (not electronic mail)
(iv) Apes and monkey:
A monkey is any member of either the New World monkeys or Old World monkeys, two of the three groupings of simian primates, the third group being the apes.
(v) Hydrostatics and hydrodynamics:
Hydrostatics:
Fluid statics (also called hydrostatics) is the science of fluids at rest, and is a sub-field within fluid mechanics
Hydrodynamics:
The branch of science concerned with forces acting on or exerted by fluids (especially liquids).
(vi) Comet and meteor:
Comet:
Any icy object that exists within the solar system. They are pieces of the primitive, unprocessed matter that formed the solar system 4.6 x 109 years ago. They are typically a few kilometers across and consist mainly of dust grains, frozen water, carbon monoxide and carbon dioxide; they contain many simple organic molecules.
Meteor:
A meteoroid is a small sand to boulder-sized particle of debris in the Solar system. The visible path of a meteoroid that enters Earth's (or another body's) atmosphere is a meteor, commonly called a "shooting star" or "falling star". Many meteors are part of a meteor shower.
(vii) Barrage and dam:
Barrage:
Not built at heights.
Pressure is not enough to produce electricity.
Only Canals are marked out of it.
Dam:
Built at heights.
Pressure is enough to move turbines so hydroelectricity is generated.
(viii) Electron and hole:
Electron:
They belong to the lepton family and are the negatively charged components of atoms (1.6 x10^-19 coulomb). In the simplest model of the atom, electrons are envisaged to move around the atomic nucleus in specified circular and elliptical orbits.
Electron Hole:
An electron hole is the conceptual and mathematical opposite of an electron, useful in the study of physics and chemistry. The concept describes the lack of an electron. It is different from the positron, which is the antimatter duplicate of the electron.
(ix) Isobars and isotopes:
Isobars:
line on a weather map or chart that connects areas of equal barometric pressure
Isotopes:
Any of the several different forms of an element each having different atomic mass (mass number). Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons.
Or
Isotopes and Isobars:
The various nuclides, or species, of a particular chemical element with equal proton number (atomic number), but different neutron numbers were called isotopes of the element, before the more inclusive term "nuclide" was internationally accepted (ca. 1950. Such particular nuclides may still be called "isotopes." However, nuclides with equal mass number but different atomic number are called isobars (isobar = equal in weight), whereas Isotones are nuclides of equal neutron number but different proton numbers.
(x)Autopsy and biopsy:
Autopsy:
Postmortem, examination of a corpse to determine cause of death
Biopsy:
Removal and study of a tissue sample for diagnostic purposes